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THE BALANCED BETA 22 BUILD LOG

beta22

THE BALANCED BETA 22 BUILD LOG

Postby Energy » October 15th, 2014, 12:36 am

 
THE BALANCED BETA 22 BUILD LOG

So it's that time of year where my fingers get itchy to build something. This year it's the β22 and σ22.
I don't plan on using the LCDuino-1, δ1, δ2, but may add it in later on if I feel that it is needed. :?

My build will be very simple. I plan to stack it on top of each other and to have it fit perfectly on my desk, thus a custom chassis is needed.
:ugeek: Below are some sketches I've made of the β22 and σ22 chassis. Feel free to use them for yourself.


:CHASSIS DESIGN:
Image

Front:
24mm hole is for the Balanced Output
10mm hole is for the Stepped Attenuator
3mm hole(s) is for LED's.
Back:
22mm hole(s) is for Power Connectors
24mm hole(s) is for the Balanced Input
24mm hole(s) is for the PreAmp Output
Top & Sides:
5mm hole(s) is for heat dissipation
Bottom:
There are no holes at the bottom of chassis when received from the supplier.
Holes will be drilled later on to accommodate the β22 boards and Stepped Attenuator.
Rubber Feet's are used beneath this chassis to separate the two enclosures giving room for heat to dissipated from chassis beneath it (σ22).

Image

Front:
3mm hole(s) is for LED's.
Back:
22mm hole(s) is for Power Connectors
66mm x 28mm Rectangular Cutout is for IEC Inlet Filter
Top & Sides:
5mm hole(s) is for heat dissipation
Bottom:
There are no holes at the bottom of chassis when received from the supplier.
Holes will be drilled later on to accommodate the σ22 boards and Transformer.
Rubber Feet's are NOT used beneath this chassis due to height restriction.


:BETA 22 Board:
Stereo Amplifier Board: Gain = 2
Parts: Elna RFS Silmic II | Vishay Dale RN55D | WIMA 1uF 100V | 5N OCC Silver 24AWG (for R30/R31) | Aavid Thermalloy Modified Heatsinks

Image
Image

:SIGMA 22 Board:
Regulated Power Supply (Linear): Dual-Rail
Parts: Nichicon HE & Panasonic FR | Vishay Dale RN55D | WIMA 1uF 100V | Semitec E-562 (for CR3/CR4) | Semitec E-202 (for CR1/CR2) | Aavid Thermalloy Modified Heatsinks

Image
Image

:STEPPED ATTENUATOR:
GoldPoint Mini-V Quad (Standard): Volume Control
Parts: 7N OCC SILVER (Litz Type 2) - Polyethylene Insulated | 105-strands

Image

:TOROIDAL TRANSFORMER:
Avel-Lindberg Y236356 (Toroidal): 2x30V 80VA
Parts CA-050 Steel Covers
These covers help to prevent the magnetic field of the transformer from radiating noise and interfering with sensitive audio components that are nearby. They are placed over the transformers to offer isolation between components

Image
Image

:IEC INLET FILTER:
Delta Electronics 06AK2D (EMI Filter): 115V/6A
Parts: Aucharm 99.9% Silver 4A Fuse

Image

:POWER CONNECTOR:
Amphenol Tuchel C016 30K006 100 12 (Circular DIN): 6-Pin Male Connector (+1 Ground)
Amphenol Tuchel C016 30G006 100 12 (Circular DIN): 6-Pin Female Connector (+1 Ground)
Since each σ22 board connects to two β22 boards, I felt that a connector with 6 usable pins was more appropriate than a connector with only 3-4. A right angle connector was chosen for a shorter power cable run.

Image
Image

:SIGMA 22 BUILD:
Both boards ready for assembly!
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Six silver-plated copper teflon wires (20AWG) are used for each σ22 board.
Each are connected to V-, G, V+ twice

Image

Each joint is soldered with Kester 5% Silver Solder.
Image

Each β22 board utilizes 3 wires (V-, G, V+).
Since one σ22 board powers two β22 boards, six total wires are needed.

Image

The bottom of the aluminum enclosures are drilled to accommodate the σ22 boards.
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The σ22 boards are mounted onto hex spacers and is soldered to the toroidal transformer's secondary wires.
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The six wires are then soldered to the 6-pins of female connectors. The configuration for this particular setup goes as followed:
Pin 1= V+
Pin 2 = G
Pin 3 = V-
Pin 4 = V-
Pin 5 = G
Pin 6 = V+
Pin 7 = Chassis Ground/Earth

Image

Both female connectors are soldered in the orientation as listed above. Each with a wire coming from Pin 7 just in case to be used for DC power cable shielding purposes.
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Once the Delta Electronics 06AK2D power entry module is inserted into the chassis the two metal surfaces makes contact thus the chassis now effectively becomes a ground.
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Pin 7 from both connectors is soldered to Earth/Chassis Ground for power cable shielding purposes.
Image

The latest revision of the board.
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An overall look of the finished work. The LED cables are then connected to both boards.
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Back-view of the power supply.
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Greenlee DM-60 multimeter set to Voltage (DC) measures ~29.3V for output V-/G & V+/G
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:BETA 22 BUILD:
Starting with the B22 board mounted with HEX risers
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I do not recommend this, but I used a single HEX riser for two boards to save on space
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Drilling a hole for the shared HEX riser to go through
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Making sure signal ground was not drilled into by accident
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Using a single hole design saves overall build width by 10-12mm
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Fitting the boards into the chassis
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Wiring the stepped attentuator
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Installing the first amplifier board
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Further fitting and drilling of holes to mount the additional boards
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Wiring things up as I go and insertion of the shaft
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All boards mounted and fully wired
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LED's cables are connected from the boards to the front panel LED's
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Neotech OCC Silver Stepped Attentuator Network (with solid silver leads for ground)
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An overall look of the finished work. The LED cables are then connected to all four boards
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Rear view of all connected wires
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Time to build the right angle power cable
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Super short power cable DIY
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Wires are coded for positive (red), negative (white), and ground (black) identification
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6-wire square braid to help lower inductance and improve aesthetics
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Measuring how much length is needed and finalizing the soldering process
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Super short cable completed for low impedance and stacking efficiency
Image
Last edited by Energy on September 24th, 2019, 2:35 am, edited 122 times in total.
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Re: BETA 22 Build Log - by Timothy

Postby Energy » November 16th, 2016, 6:20 pm

It's been awhile. I'm coming back now with some free time to resume this build.
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Re: BETA 22 Build Log - by Timothy

Postby kt88 » November 16th, 2016, 9:39 pm

Keep posting, looking good.

I'm also in the process of building a B22, although mine will be used with speakers as well, so my case is used as a HS (it has large radiators on the sides). Oh, and I'm also doing it a single case build. Somehow I find it more satisfying to have all in a single case, feels more organized to me. Just like you, finding the time is the more difficult part of the build :)
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Re: BETA 22 Build Log - by Timothy

Postby linux-works » November 17th, 2016, 7:54 am

just an idea, but the sercona 4" preamp board might fit inside and would give you a solid state volume control, remote control and a display. you could probably build it for about the cost of the passive stepped atten, too ;)

fwiw
Sercona Audio (Control Systems for Analog and Digital)
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Re: BETA 22 Build Log - by Timothy

Postby Energy » November 21st, 2016, 2:01 am

kt88 wrote:Keep posting, looking good. I'm also in the process of building a B22, although mine will be used with speakers as well, so my case is used as a HS (it has large radiators on the sides). Oh, and I'm also doing it a single case build. Somehow I find it more satisfying to have all in a single case, feels more organized to me. Just like you, finding the time is the more difficult part of the build :)

Come join the fun! :P If you're looking for transformers for your o22 let me know. I have two in new condition. They're 100VA with 30V secondary. I bought them, but soon realized they're too large for my toroidal transformer cover. I'm stacking the B22 over the O22 so having the cover is necessary to prevent hum.

linux-works wrote:just an idea, but the sercona 4" preamp board might fit inside and would give you a solid state volume control, remote control and a display. you could probably build it for about the cost of the passive stepped atten, too ;)

fwiw

I would love to! But one unfortunate thing is that I already have the passive stepped attenuator in hand. It's hard to sell and if it sells, goes for way below the retail cost I paid for.
Last edited by Energy on November 21st, 2016, 7:08 am, edited 1 time in total.
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Re: BETA 22 Build Log - by Energy

Postby amb » November 21st, 2016, 4:02 am

ohsnaptimothy is now known as Energy on this forum.
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Re: BALANCED BETA 22 BUILD LOG - by ENERGY

Postby therobbstory » November 23rd, 2016, 12:28 pm

oh snap.
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Re: BALANCED BETA 22 BUILD LOG - by ENERGY

Postby MASantos » November 25th, 2016, 1:48 pm

I believe you should only have one ground connection between the o22 and b22 boards, not one for each board. Having 4 ground return wires in the umbilical cables might create ground loop problems.
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Re: BALANCED BETA 22 BUILD LOG - by ENERGY

Postby amb » November 25th, 2016, 9:26 pm

In a system with independent transformers and σ22s for each channel, the grounds between the channels should be kept separate in order for it to be a true dual-mono configuration. As for the grounds between the hot and cold sides on each channel, I recommend the following scheme. The place where V+/G/V- join together can either be within the amp chassis or the power supply chasses. The former requires less wires in the umbilical cable and is thus more convenient.

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Re: BALANCED BETA 22 BUILD LOG - by ENERGY

Postby Energy » November 27th, 2016, 6:00 pm

For a short DC power cable run from the PSU to the amplifier of roughly 1 foot, is shielding (connected to PSU ground) necessary? The power cable may come in contact with XLR cables.

That said, is it necessary to ground the PSU to the Amplifier chassis via shielded power cable from the PSU to the amplifier?
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